Instructions

Combination

All applicants who are applying for a Class A CDL should be prepared to take the Combination test. This test covers information found in Section 6 of the Texas Commercial Motor Vehicle Drivers Handbook. Section 6 provides the information needed to safely operate tractor-trailers, doubles, triples, and straight trucks with trailers. The test is made up of 20 multiple-choice questions, and applicants will need to correctly answer a minimum of 16 questions to pass. The Combination test is not a replacement for the Double/Triple endorsement test.

Number of Question 20

Passing Score 16

1. What is a tractor protection valve?

A valve to keep air in the brake system should there be a bad leak

A valve that prevents the truck from being stolen

A valve that prevents the driver from going too fast

A valve that prevents the trailer from accidentally being released

In a combination vehicle with air brakes, the tractor protection valve keeps air in the tractor or truck brake system in the event of the trailer breaking away or developing a leak.

2. To help prevent rollovers, you should:

Accelerate quickly after stopping.

Drive slowly around turns.

Keep the load near the back of the trailer.

Keep the load on one side of the trailer.

To lower the risk of a rollover, load your cargo as closely to the ground as possible. To further reduce this risk, take curves and corners slowly.

3. When coupling a trailer:

Make sure to couple matching glad hands.

Any glad hand can be connected to any other glad hand.

It is best to leave one glad hand unattached.

Only one set of glad hands should be connected.

When coupling, make sure you couple matching glad hands. They are often color-coded to help drivers avoid mistakes. Typically, blue is used for service lines and red is used for emergency lines.

4. Rollovers happen when:

A truck driver is driving too fast.

The driver of a vehicle in front of a truck is moving to slowly.

A truck driver is driving too slowly.

ABS is working effectively.

Rollovers happen when a vehicle is driven too fast. To reduce the risk of rollover, make sure the weight of cargo is loaded low to the ground, and that you take turns and curves slowly.

5. The service air line is attached to the:

Relay valves.

Supply line.

Emergency air line.

Steering wheel.

The service air line carries air and is controlled by either the foot brake or trailer hand brake. The service air line is attached to relay valves, which allow the trailer brakes to be applied quickly.

6. When driving a bobtail tractor, you should be aware that:

Bobtails stop very easily.

Bobtails cannot drive as fast as tractors with semitrailers.

Bobtails are more difficult to stop than tractors with semitrailers.

Bobtails are illegal in most states.

Bobtail tractors are tractors that are not attached to any semitrailers. When operating a bobtail, you should be aware that stopping can be difficult and that it will take a longer distance to bring the bobtail to a complete stop than it would a tractor attached to a loaded semitrailer.

7. Large combination vehicles take the longest amount of time to stop:

When fully loaded.

When partially loaded.

When empty.

When mostly loaded.

Large combination vehicles take longer to stop when they are empty than when they are loaded. The decreased weight causes a vehicle's wheels to have decreased traction on the surface of the road.

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